Gold nanoparticle (“NP”)-based colorimetric detection exploits the readily detectable color change that occurs upon NP aggregation. In some instances, NPs with appropriate surface functionalization provides for a simple and inexpensive method for sensing an expanding range of analytes such as nucleic acids, biomolecules, organic molecules, and metal ions. Gold NP-based detection methods provide several potential advantages over other techniques because 1) gold NPs have high extinction coefficients, which translates to a stronger signal and high sensitivity and 2) their color change can be detected without instrumentation.
Despite these advantages, the most common methods for nucleic acid sensing remain using fluorescent dyes and polymerase chain reaction (PCR), primarily because conventional implementation of gold NP-based in colorimetric detection restricts the sensitivity of the method. This limited sensitivity may be overcome, in some instances, by additional amplification steps. However, these additional steps undermine the simplicity of the conventional detection methods.